Field of the Invention
The present invention relates to a toner to be used in an image-forming method for visualizing an electrostatic charge image in electrophotography.
Description of the Related Art
In recent years, an image-forming apparatus, such as a copying machine or a printer, has been required not only to provide high image quality but also to have both a longer lifetime and a smaller size.
A possible approach to downsizing the image-forming apparatus (in particular, the printer) is a reduction in diameter of a toner carrier or elimination of a supply roller for supplying the toner carrier with a toner. In the case of reducing the diameter of the toner carrier, the toner carrier has an increased curvature, which results in a reduced area of a region of contact between the toner carrier, to which an electric charge is imparted, and a developer-regulating member (hereinafter referred to as “regulating portion”). This condition is severe for imparting the electric charge in the regulating portion. In addition, in the case of eliminating the supply roller, a property of conveying the toner to the toner carrier becomes poor, and hence it is difficult to uniformly convey the toner to the regulating portion. This condition is severe for uniformly imparting the electric charge.
In addition, in recent years, use of the copying machine, the printer, and the like has been rapidly increasing in emerging countries. Countries classified as emerging countries often have an environment having a much higher temperature and a much higher humidity as compared to developed countries. Accordingly, the toner in a cartridge is liable to adsorb moisture, and there is a concern for an adverse effect on an image due to charging failure.
In view of the foregoing, it is necessary to solve problems which may arise when, in the future, a downsized printer is placed under a high-temperature and high-humidity environment and used under various conditions for a long period of time. In this regard, various toner-improving methods have heretofore been proposed.
In Japanese Patent Application Laid-Open No. 2011-13441, it is disclosed that a layered inorganic mineral is added to toner particles to suppress exudation of a release agent to their surfaces, with the result that an inter-toner cohesive force can be reduced and charging performance can be stabilized even in a high-temperature region.
In Japanese Patent Application Laid-Open No. 2007-322919, it is disclosed that when large-particle-diameter silica particles having a sharp particle size distribution obtained by a sol-gel method are used for the toner, stable chargeability can be obtained over a long period of time.
In Japanese Patent Application Laid-Open No. 2012-118541, it is disclosed that the number of silanol groups of large-particle-diameter silica having a sharp particle size distribution is reduced to improve flowability of the toner irrespective of the environment, and thus stable charging performance is obtained.
In Japanese Patent Application Laid-Open No. 2012-63636, it is disclosed that an alkylsilane is used for surface treatment of silica to improve charging performance.